[Boatanchors] Running European 230 VAC on our AC

[Glen Zook]

The neutral is NOT 120 VAC above ground!  That assumes that one side of the 240 VAC is grounded which is not the case in this country.  The secondary on the "pole pig" (distribution transformer) is center tapped with 120 VAC on either side of the center tap.  The connection to this center tap is the neutral.

At the entrance to the building, the connection to the neutral is grounded by an external connection usually to a ground rod driven near the entrance point.  This puts the neutral basically at "ground" potential.  In 240-volt 3-wire systems (no longer approved for new installations) all 3-wires coming from the pole pig continue to the load.  In 240-volt 4-wire systems there is an additional "ground wire" which is connected to the point at which the neutral connects to the external ground rod.

For the 120 VAC distributed within the building, one side of the 240 VAC and the neutral are involved which gives 120 VAC.  Then, a ground wire is added for safety.
 
Glen, K9STH


Website:  http://k9sth.com


________________________________
 From: Sheldon Daitch <sdaitch at kuw.ibb.gov>
To: 
Cc: "boatanchors at mailman.qth.net" <boatanchors at mailman.qth.net> 
Sent: Sunday, October 21, 2012 5:06 AM
Subject: Re: [Boatanchors] Running European 230 VAC on our AC
 
As noted, some 240VAC US appliances do need the neutral
to pick up the 120VAC for some 120VAC applications in the
unit.

We have a US built stove which the manufacturer has to add a
stepdown transformer for the export model, since the 230VAC
systems outside the US typically do not have the neutral
centertap.

In our stove, that stepdown transformer was an autotransfomer,
not an isolation transformer and it failed.  I discovered that the
way the transformer was wired and the stove was wired into
our 230VAC system that the common of the autotransformer
was wired to the high leg of the wiring and perhaps that was
the cause of the eventual failure of the transformer.

I bring this up, as running  230VAC equipment which is designed
for a hot and neutral might have some problems if the neutral
leg is actually 120VAC above ground.  In theory, no, but with
polarized systems, the powered unit is normally going to see
near-ground voltage outside the US, but in the US, the neutral
leg would be 120VAC above ground.

(One interesting aspect of many 230VAC systems outside the
US is that many residential systems are three phase, and
with 230VAC phase to neutral, phase to phase voltages are
in the 400VAC range.)